MAKE Magazine subscriber Jeremie Boulianne of Calgary, Alberta, came with a unique way to build a linear actuator:

Linear actuation is an elusive and expensive field to get into but I always seem to find a need for it with robots I build. Whether it being to raise a turret or dispense a marker a linear actuator would be so handy.

My proof-of-concept solution (hack) was to create a linear actuator design that is accessible to even electronics enthusiasts on the tightest budget. Using a common item, that I hope everyone uses :), you can build one yourself after the product has been used up. I recommend leaving the dispenser under hot water for a few minutes and then use an old toothbrush to clean off the remaining residue before you hack it. The amount of travel for this plastic worm gear assembly is a tad over 3 inches. Right now I don’t have an installed solution for detecting end of travel but I would assume it’d be easy enough to add a Freeduino with some limit switches or current sensing chips. The Freeduino could also drive your servo signal at the same time…BONUS!